A flat object unstacking device comprises four main units:
a mail feed magazine, PA1 a mail holding device, PA1 a double pick separator, PA1 a transfer or take-off device.
The mail is stood on edge on a belt with its back against a plate. The belt and the plate are driven simultaneously so that the mail is moved towards the holding device. The belt leads to a sudden change in level, referred to hereinafter as the drop, near the mail holding device. The feed magazine is between the drop and the holding device and is adapted to receive the mail items or flat objects pending unstacking. The holding device has suction areas across which a perforated belt passes.
On leaving the holding device the mail passes in front of the suction area of the double pick separator on the opposite side of the belt. This unit retains mail items that might otherwise be entrained by friction by the preceding mail item so that only one mail item at a time can leave.
On leaving the double pick separator the mail is taken into a transfer device which constitutes an interface between the unstacking device and a sorting device.
Large mail items are sorted by placing them in buckets, so unstacking must be on demand rather than continuous.
It is also necessary to stop the mail almost immediately when it enters the transfer device. The conventional means of achieving this halt the mail very unevenly because of substantial bouncing of thick mail items leading to loss of contact with the mail item at the point where it should be halted.
French patent application No 91 09431 of 25 Jul. 1991 in the name of this Applicant discloses a device for unstacking mail items having at its output mail item transfer means comprising two associated belts with a gripping action. These means cannot transfer objects of varying thickness, however, and operate continuously.